Facebook turns to solar for heat and power

Facebook plans to build a solar system on the rooftop of its headquarters in Menlo Park, Calif., from startup Cogenra Solar, that will generate both electricity and heat. The system will be built on the company’s fitness center and in addition to electricity, will provide heat for the showers and will displace 60 percent of the building’s natural gas needs.

Cogenra is a VC-backed Valley startup that has designed a hybrid solar system that uses both mirrors and solar cells to generate electricity and useful heat. The system uses a single-axis tracker, and relies on glass mirrors to concentrate sunlight onto silicon solar cells to produce electricity. In the same region where the cells reside is a fluid-containing tube that absorbs the heat produced from the process of electricity production.

The fluid, a glycol mixture that is freeze-resistant and commonly used to transfer heat in cars and liquid-cooled computers, is then piped to a holding tank for heating water (see diagram below). In settings that require hot water around the clock, a boiler remains necessary for the final heating.

CEO Gilad Almogy founded the company (previously called SkyWatch Energy), and Congenra has raised at least $10.5 million from investors and counts Khosla Ventures among its backers. Cogenra has also installed a 272-kilowatt system at the Sonoma Wine Company in Graton, Calif.

A panel filled with silicon solar cells typically can convert around 16 percent of the sunlight that falls on it into electricity. The rest of the solar energy becomes heat, which is commonly dissipated and can also threaten the performance of solar cells. A growing number of companies, like Cogenra, PVT Solar, Cool Energy and Conserval Engineering, are looking at ways to make use of the heat, while also generating electricity. Cogenra’s system can turn 75 percent of the solar energy into useful electricity and heat.

Internet and clean power

Internet giants are starting to pay closer attention to clean energy, as both a new source of electricity for their power-hungry data centers, as a PR opportunity, and as a way to save money on power costs for their operations. Google put solar panels on its rooftop several years ago. Facebook says it’s the first of its peers to embrace this type of hybrid solar design.

Facebook says the Cogenra solar system has less than a fiv- year payback period, which is significantly shorter than many traditional solar rooftop systems.

Solar systems built near data centers have gained prominence this year, too. Apple has plans to build a solar system next to its mega data center in Maiden, N.C., which will partly power iCloud. Google has invested hundreds of millions in clean power projects — both wind and solar — in an effort to boost the market for clean power and also to make a long-term low-risk return (solar projects can deliver something like 12 percent return over 20 years).

As Greenpeace has said before, Internet giants — in particular consumer-facing brands like Facebook and Apple — can use their prominence, leadership and large balance sheets to build new clean power systems and also ask utilities for clean power when they construct their data centers.